Control for hydraulic apparatus



Jan. 30, 1968 w. T. STEPHENS ET AL 3,366,064

CONTROL FOR HYDRAULIC APPARATUS 2 Sheets-Sheet 1 Filed March 10, 1965 1963 w. T. STEPHENS ET AL 3,366,064

v CONTROL FOR HYDRAULIC APPARATUS 2 Sheets-Sheet 2 Filed March 10, 1965 fizz/6721 5715: j

racicz 121/: (limb/ W United States Patent 3,366,064 CONTROL FOR HYDRAULIC APPARATUS William T. Stephens, Mentor, Ohio, and Gerald F. Randa, Auburn, Ind., assignors to Borg-Warner Corporation, Chicago, Ill., a corporation of Illinois Filed Mar. 10, 1965, Ser. No. 438,566 9 Claims. (Cl. 10338) ABSTRACT OF THE DISCLOSURE Hydraulic apparatus includes a variable displacement pump, a control for the pump and a working circuit supplied by the pump. The working circuit includes a closed end main conduit and a pilot conduit supplied by the main conduit through an orifice, the pilot conduit returning to sump. A bank of tandem control valves is connected to both the main and pilot conduits such that connection of a single load will block flow in the pilot conduit while a number of loads may be connected to the main conduit at the same time. The pump control is arranged to shift from idle to operating condition responsive to blockage of flow in the pilot conduit and to thereafter increase the pump flow rate as additional loads are connected. Means are provided for shifting the pump to different operating characteristics when particular loads are connected.

This invention relates generally to a pump control and more particularly, to a control which regulates pump output in accordance with the demand of circuits connected to the pump.

Hydraulic apparatus is often constructed and arranged such that a single prime mover and pump supply fluid to a number of hydraulic circuits which may be operated singly or in combination to control the movement of various machine elements. This arrangement of hydraulic apparatus may impose severe operating conditions on the pump and prime mover where some of the individual circuits have critical requirements of pressure, flow rate and the like. Combinations of circuits may tend to overload and stall the prime mover. Further, it is desirable to operate the entire apparatus without shutting down the pump and prime mover while no control functions are being performed, however, it is desirable, in such instances, to reduce the load on the pump and prime mover to the minimum.

One example of such an application is in a tractor type combination excavating machine which has a loading and dumping bucket operable on one end, and a back hoe trenching device on the opposite end. Such a machine requires the use of several control circuits. One such circuit would provide floating control for the bucket when used to scoop up loose material such as dirt fill. Quite different requirements of pressure and flow rate would be required when the full bucket is elevated for lifting and transfer of material. Still other circuit conditions would be required when the elevated bucket is tipped to unload the material.

In the operation of the back hoe portion of the machine, typical control functions might include the elevation of a boom, extension and retraction of a dipper, tipping of the excavating scoop, and swinging the assembly from side to side. It is evident that when the excavating scoop is digging into new ground the control circuit must ice supply the highest possible pressure in order to effect digging, and the maximum flow rate consistent with the capacity of the prime mover in order to accomplish its work as quickly as possible. It is also evident, that where several control functions are performed simultaneously, while the machine is in the unloaded condition, it would be desirable to provide a large flow rate while the pressure requirement would not be critical. Still other control functions might require low flow, such as where a single function is to be carried out smoothly, avoiding erratic motion and overtravel.

Accordingly, it is a principal object of this invention to provide improved means for varying the output characteristics of a pump in accordance with the demands of particular circuits and combinations of circuits connected thereto.

Another object is to provide improved means for controlling a pump which allows the apparatus to operate in a no-load or idling condition and which is capable of automatic adjustment to meet the circuit demand when loads are imposed on the apparatus.

A further object is to provide a control which auto matically restricts the operation of the pump to predetermined portions of its operating range in response to connection of particular control circuits.

A still further object is to provide control means effective to convert a variable flow pump to constant flow operation in response to the connection of predetermined circuits.

These and other objects and advantages of the invention will appear more clearly from the following description together with the drawings in which a preferred form of the invention is shown.

In the drawings:

FIGURE 1 is a schematic circuit diagram showing the interconnection of hydraulic apparatus according to the present invention;

FIGURE 2 is an enlarged fragmentary View of a control means for controlling the pump;

FIGURE 3 is an enlarged fragmentary detail of a portion of the valve means shown in FIGURE 1; and

FIGURE 4 is a graph of the pump delivery characteristics showing available relationships of flow rate and pressure provided by the control of the present invention.

Referring now to the drawings and particularly to FIG- URE 1 thereof, hydraulic apparatus is shown in which the fluid delivered by the pump is divided between a main supply conduit and a pilot conduit, both of which are connected to a plurality of control valves, the main conduit being close-ended after the last control valve while the pilot conduit continues onward to the sump. As shown more particularly in FIGURE 3, the control valves are so constructed and arranged that flow is permitted in the pilot conduit when the valve is not actuated and is blocked when actuated. Thus since the main supply conduit is close-ended, fluid can flow in either the main or pilot conduit depending upon whether a valve is actuated or not, but cannot fiowin both conduits simultaneously. As shown more particularly in FIGURE 2, the flow condition in the main and pilot conduits are applied to a pump control for regulating the output of the pump in accordance with circuit requirements.

Referring now to FIGURE 1 in more detail, the reference numeral 10 indicates generally a variable flow rate pump which may be of the swash plate type. A control lever 11 is connected to the pump for regulation of the flow rate as it is moved about its pivotal axis 12,. As shown, clockwise rotation of lever 11 results in minimum flow rate while counterclockwise rotation results in maximum flow rate. Outlet port 13 of pump is connected to a main supply conduit 14- for conducting pressure fluid in the circuit. Main supply conduit 14 is connected to branch conduit 16 and to a bank of control valves 17 shown in FIGURE 3. Branch conduit 16 is connected to the pump control means 39 in FIGURE 2. A pressure limiting relief valve 18 within valve bank 17 is connected between main conduit 14 and return conduit 1%.

As shown diagrammatically in FIGURE 1, main conduit 14 continues through valve bank 17 to and through a second valve bank 21 where it is close-ended by plug 22. Respective driven devices 31498 are connected in parallel with each other between main conduit 14 and return conduit 19 by respective control valves 23-30. This arrangement permits the driven devices to be connected to supply conduit 14 either singly or in combination and for either forward or reverse motion. Since main conduit 14 is closeended at 22, it is evident, that when all of control valves 2330 are in neutral position, the output of the pump must flow through branch conduit 16 to and through control means 39 and pilot conduit Pilot conduit 41 is con-- nected through control valves 23-30 in series relationship such that when all control valves are in neutral, flow is permitted to return to sump 43 through banks 17 and 21, pilot return line 42, and the pump casing. Since pilot conduit 41 is connected to branch conduit 16 through orifice 44, the flow rate in pilot conduit 41 is less than the available flow rate in main conduit 14. Under these conditions, orifice 44- also reduces the pressure of the fluid flowing in pilot conduit 41. Thus, when all of control valves 23-30 are in neutral condition, fluid within the portion of conduit 14 in the valve bank, is static but at high pressure, while low flow at low pressure exists in pilot conduit 41.

When any of control valves 23-38 are actuated, pilot conduit 41 is blocked, and main conduit 14 is connected to a corresponding driven device. This results in a pressure drop in main conduit 41. When one or more of these valves is actuated, the circuit requires a greater rate of flow to supply the driven device. When all control valves are in neutral, the pump need deliver only the flow rate required by pilot conduit 41.

The changes in flow rate and pressure in main conduit 14 and pilot conduit 41 are made use of in control means 39 to shift the pump from one mode of operation to another to meet the changes in circuit demands. For example, the pump can be shifted from idling condition to full flow condition when a load is connected. Other control functions can be effected through control lines 46 and 47 connected between portions of pilot conduit 41 and control means 39.

Referring now to FIGURE 3, control valves 27 and 23 are shown somewhat diagrammatically to illustrate the flow ot' fluid in main conduit 14, pilot conduit 41 and control line 47. Spool 48 in valve 27 is shown in the neutral position while spool 49 in valve 28 is shown in one of its actuated positions. In the neutral position, spool 43 has a land 51 which permits flow through valve 27 into valve 28, but, prevents flow to a driven device through either of ports 52 or 53. Spool 48 has pilot lands 54, 55 and pilot groove 56 which permit flow from pilot conduit 41 through valve 27 into valve 28.

Spool 49 of valve 28 is shown in one of its actuated positions. In the actuated position, land 57 has been moved to permit flow from main conduit 14 to port 59 and to allow flow from port 58 to return conduit 19. In the actuated condition, land portion 61 blocks passage of fluid in pilot line 41. If spool 49 were moved in the opposite direction, the effect would be to reverse the connections of ports 58 and 59 so that port 58 would be connected to main conduit 14 and port 59 would be connected to return conduit 19. In this condition, pilot land 62 would overlap the pilot passage to block flow in pilot conduit 41. Thus, any time full flow is permitted in main conduit 14, the pilot conduit 41 is blocked.

When flow is blocked in pilot conduit 41, the pressure of the fluid therein increases to pump output pressure since there is no flow across orifice 44. Connection of a control line 47 to the pilot passage within a selected control valve provides a source of high pressure fluid for performing control functions associated with the operation of that particular valve. Thus when control valve 28 is actuated in either direction, control line 47 is supplied with fluid under high pressure. Control line 47 is connected to control means 39 for selecting a delivery characteristic of pump 1% consistent with the circuit connected to valve 28. The pilot passage can be tapped between valve bank 17 and 21 to pressurize a second control line 46 in response to actuation of either control valve 29 or 30. Control line 46 is also connected back to the control means 39 for selecting a particular delivery characteristic of the pump consistent with the demands of circuits connected to valves 29 or 36.

Referring now particularly to FIGURE 4, a graph of the pump delivery characteristics is shown. Upper hori zontal line 63 indicates the condition in which control lever 11 is in its maximum counterclockwise position. In this condition the pump delivers a predetermined volume per revolution, regardless of pressure. The knee point 64 separates the constant volume portion of the pump characteristic from variable delivery portion in which the flow delivered by the pump varies in response to the pressure. Variable delivery portion 66 termi.1ates at cut off point 67 which corresponds to a preselected minimum flow or idling condition. In idling condition, the fluid supplied by the pump is sufiicient to provide the pilot flow through conduit 41, and make up for any leakage that might occur elsewhere in the system. Horizontal lines 68 and 69 represent optional constant flow characteristics corresponding to particular circuit functions. These characteristics are selected by pressurizing control line 46 or 47.

Referring now to FIGURE 2, pivotal control lever 11 is connected to regulate the delivery of pump 10. A bias piston 71 is longitudinally slidable in bore 72. Spring 73 urges piston 71 against control lever 11. Bore 72 communicates directly with branch 16 of main pressure conduit 14 so that the full pressure output of the pump bears upon bias piston 71 to urge control lever 11 clockwise toward the minimum delivery position.

Branch conduit 16 is connected to pilot conduit 41 by orifice 44. Since fluid is permitted to flow from conduit 16 across orifice 44 to pilot conduit 41 a pressure drop is developed in pilot conduit 41. Sensor piston 76 is acted upon by the fluid pressure existing in pilot conduit 41. Piston 76 bears on a ported sensorspool 77 which is longitudinally slidable in spool guide bore 78. Sensorspool 77 has a pair of ports 79 and 81 connected by passage 82. Fluid admitted to port 79 may be conducted to the casing of pump 10 which is at the low pressure of return line 42. Movement of sensorspool 77 is opposed by calibrated sensor spring 83 which bears against and senses the position of control lever 11.

Movement of bias piston 71 is balanced by actuator piston 84 in bore 87 bearing against control 11 through link 86. Bore 87 also communicates with pilot conduit 41 through a second orifice 88. While fluid is flowing across orifice 88, the pressure on actuator piston 84 is less than the pressure in pilot conduit 41. When a pre selected combination of control lever position and pilot conduit pressure occurs, sensorspool 77 will be moved longitudinally to the left as viewed in FIGURE 2. In this position, port 7 will uncover passage 89 permitting fluid to flow away from actuator piston 84 into the pump casing. This results in flow across the second orifice to further reduce the pressure acting on actuator piston 84.

Since bias piston 71 urges control lever 11 in the opposite direction, actuator piston 84 will be moved to the right to establish equilibrium. Pressure variations in main conduit 14 permit control lever 11 to operate at positions intermediate its minimum and maximum flow position as indicated :by sloping line 66 of FIGURE 4.

When lever 11 is in its maximum counterclockwise position, the pump operating characteristic is represented by constant volume line 63 in FIGURE 4. A pair of stops 91 and 92 are provided for limiting the angular motion of control lever 11. These stops are shown in the form of tandem pistons operable respectively in bores 93 and 94 in response to pressure in control lines 46 and 47. While this tandem arrangement may be advantageous in some applications, a pair of independent stops could also be used. Actuation of these stops results in a pump characteristic indicated by lines 68 and 69 of FIGURE 4.

Operation When all control valves are in neutral and the pump is turned on, the pressure immediately increases in conduits 14 and 16 to the value established by relief valve 18. For example this pressure could be 3,000 p.s.i. This pressure acts on bias piston 71 to rotate control lever 11 to its minimum flow rate position. As fluid flows through orifice 44 into pilot conduit 41, pressure in conduits 14, 16 and bias piston bore 72 will be reduced, for example, to 2500 p.s.i. while pressure in pilot conduit 41 is reduced to 2000 p.s.i. Since sensor piston 77 is moved to the right under these circumstances, there is no flow through passage 89 or orifice 88. Therefore a pressure of 200' p.s.i. acts upon bias piston 71. The difference in pressures and piston diameters results in control lever 11 moving slightly from minimum position to idling position in which operation is stabilized at, for example, 3 gallons per minute at 2500 p.s.i. This condition is illustrated in FIGURE 4 at point 67.

If one or more of control valves 23-27 are actuated, fluid is allowed to flow out of the main conduit resulting in a pressure drop. For purposes of illustration, let us assume, the pressure drops to 2000 p.s.i. Under this condition, pressure on bias piston 71 drops from 2500 p.s.i. to 2000 p.s.i. while pressure on actuator piston 84 increases from 200 p.s.i. to 2000 p.s.i. resulting in counterclockwise movement of control lever 11 to increase the flow rate of the pump.

As actuator piston 84 moves to the left, flow exists across orifice 88 with the result that the instantaneous pressure of 2000 p.s.i. is reduced. However, the full line pressure remains on sensor piston 76 moving it to the left as viewed in FIGURE 2 until port 79 is in position to release fluid from bore 87. This combination results in stabilization of the pump control for delivery of, for example, gallons per minute at 2000 p.s.i.

If additional circuits are connected by actuation of additional control valves, the main conduit pressure will drop further, for example, to 1500 p.s.i. Under this condition the pressure on sensor piston 76 will drop from 2000 p.s.i. to 1500 p.s.i. resulting in movement of sensorspool 77 toward the right to block passage 89. This in turn, stops fiow across orifice 88 which increases the pressure acting on actuator piston 84 to move it and control lever 11 toward the left. This allows sensor spring 83 to extend, thereby reducing the force on sensor spool 77. Spool 77 then moves toward the left until port 79 again overlaps passage 89. Proper operation is then stabilized at a new level represented by knee point 64 of FIGURE 4, corresponding to 15 gallons per minute at 1500 p.s.i. The position shown in FIGURE 2 for the various components correspond to operation at knee point 64.

After control lever 11 moves to its maximum counterclockwise position further reduction of pressure has no bearing on the flow rate. This results in constant flow operation corresponding to line 63 of FIGURE 4.

Where it is desired to impose an arbitary maximum 6 flow characteristic of the pump illustrated by line 68 or 69 of FIGURE 4, the pilot passage 41 can be tapped in one or more of the control valves to pressurize a control line such as line 47 in valve 28.

When the valve is actuated, line pressure will act on stop piston 92 through pilot conduit 41 and control line 47. Stop piston 92 moves toward the left, in FIGURE 2, to limit the travel of control lever 11. This provides an optional constant flow operating mode for the pump. Thus when particular control valves are actuated, the pump will go into a preselected constant flow mode of operation, regardless of further pressure drop in main conduit 14.

While we have shown and described a preferred form of our invention, various changes and modifications may be made within the spirit of the invention and the scope of the following claims.

What is claimed is:

1. In hydraulic apparatus:

a pump having a pressure port;

a control device for regulating the delivery of said a pressure conduit connected to the pressure port of said pump;

valve means connected to said pressure conduit effective to control fluid flow therein;

a pilot conduit connected to said valve means, adapted to sense fluid flow conditions in said pressure conduit;

bias means engaged with said control device and connected to said pressure conduit urging said control device in one direction in response to pressure in said pressure conduit;

actuating m ans engaged with said control device and connected to said pilot conduit urging said control device in the other direction responsive to pressure in said pilot conduit; and

sensor means engaged with said control device, and connected to said pilot conduit and said actuating means, adapted to modify the movement of said actuating means in response to a predetermined combination of control device position and pressure in said pilot conduit.

2. In hydraulic apparatus:

a pump having a pressure port;

a control device for regulating the delivery of said a pressure conduit connected to the pressure port of said pump;

a pilot conduit;

a restricted passage connected between said pressure conduit and said pilot conduit;

valve means connected to both said pressure conduit and said pilot conduit;

bias means engaged with said control device and connected to said pressure conduit urging said control device in one direction in response to pressure in said pressure conduit; Y

actuating means engaged with said control device and connected to said pilot conduit urging said control device in the opposite direction responsive to pressure in said pilot conduit; and

sensor means engaged with said control device and connected to said pilot conduit and said actuating means, adapted to modify the movement of said actuating means in response to a predetermined combination of said control device position and said pilot conduit pressure.

3. In hydraulic apparatus:

a variable volume pump having a pressure port;

a movable control device connected to said pump effective to control the delivery characteristics of said pump upon movement thereof;

a pressure conduit connected to the pressure port of said pump;

a pilot conduit;

a restricted passage connected between said pressure conduit and said pilot conduit;

valve means connected to said pressure conduit and said pilot conduit effective to block flow in said pressure conduit while permitting flow in said pilot conduit under one condition of operation and permitting flow in said pressure conduit while blocking flow in said pilot conduit under another condition of operation;

bias means engaged with said control device and connected to said pressure conduit urging said control device in one direction in response to the said one condition of operation;

actuating means engaged with said control device and connected to said pilot conduit urging said control device in the opposite direction in response to the said other condition of operation; and

sensor means engaged with said control device and connected to said pilot conduit and said actuating means, adapted to modify the movement of said actuating means in response to a predetermined combination of control device position and pressure in said pilot conduit.

4. In hydraulic apparatus:

a variable volume swash plate pump having a pressure port:

an angularly moveable control device connected to the swash plate of said pump effective to vary the delivery of said pump upon pivotal movement thereof;

a pressure conduit connected to the pressure port of said pump;

a pilot conduit;

a restricted passage connected between said pressure conduit and said pilot conduit normally limiting the flow of fluid through said pilot conduit;

valve means connected to said pressure conduit and said pilot conduit effective to block flow in a portion of said pressure conduit while permitting flow through said pilot conduit under one condition of operation and permitting flow in said pressure conduit while blocking flow in said pilot conduit under another condition of operation;

bias means engaged with said control device and connected to said pressure conduit urging said control device toward a position to limit the delivery of said pump in response to blocking of flow in said pressure conduit;

actuating means engaged with said control device and connected to said pilot conduit urging said control device in the opposite direction in response to blocking of flow in said pilot conduit; and

sensor means engaged with said control device and connected to said pilot conduit and said actuating means, adapted to regulate the angular movement of said swash plate in response to a predetermined combination of control device position and pressure in said pilot conduit.

5. Apparatus according to claim 4 in which said actuating means comprises a piston and cylinder connected to said pilot conduit, and in which said sensor means comprises a bodily shiftable member urged in opposite directions by a calibrated spring bearing against said control device and a piston communicating with said pilot conduit, said member having a port adapted to relieve pressure from said actuating means cylinder in certain preselected positions of shifted movement.

6. In hydraulic apparatus:

a variable volume pump having a delivery port;

a moveable control device connected to said pump effective to decrease the delivery of said pump upon movement in one direction and to increase the delivery of said pump upon movement in the pposite direction;

a fluid supply conduit connected to the delivery port of said pump; 6

a pilot conduit connected to said supply conduit by a restricted passage;

valve means connected to said supply conduit and said pilot conduit including a plurality of control valves, said control valves being connected in parallel relationship to said supply conduit for selective distribution of fluid to a plurality of driven devices from the common supply conduit, said control valves also being connected in series relationship to said pilo conduit;

bias means bearing on said control device and connected to said supply conduit urging said control device in a direction to a decrease pump delivery, the bias effected by said means being proportional to the pressure in said supply conduit;

actuating means connected to said pilot conduit and bearing on said control device in opposition to said bias means, said actuating means overcoming the bias of said bias means to increase pump delivery in response to the pressure drop in said supply conduit when additional drive devices are connected to said supply conduit; and

sensor means moveable along a path in response to movement of said control device having a port communicating with said actuating means along a portion of said path, effective to deactivate said actuating means when said control device is moved to a predetermined maximum delivery position.

7. In hydraulic apparatus:

a variable volume pump;

a moveable control device for said pumpeifective to increase the delivery of said pump upon movement in one direction;

a pilot conduit connected to said pump;

valve means connected to said pump and to said pilot conduit including a plurality of control valves connected to respective driven devices, effective to increase fluid pressure in said pilot conduit upon actuation of any one of said control valves;

a stop member moveable to a position to limit movement of said control device in said one direction, said stop member being moveable in response to actuation of pre-selected control valves; and

actuating means bearing on said control device, urging said control device in said one direction to engage said stop member in response to an increase of pressure in said pilot conduit; and

sensor means, bodily shiftable along a path toward and away from said control device, having a port communicating with said actuating means along a pre-selected portion of said path and having a resilient spacer bearing on said control device, effective to deactivate said actuator means when said control means is bearing against said moveable stop memher.

8. In hydraulic apparatus:

an adjustable pump;

a moveable control for said pump effective to modify the delivery of said pump in accordance with the position of said control;

a fluid operated bias piston urging said control in one direction;

an inlet fluid pressure passage communicating with said bias piston;

an outlet fluid passage;

an Orifice interconnecting said inlet and outlet passages;

a fluid operated actuator piston communicating with said outlet passage urging said control in the other direction; and

a moveable sensing device including a sensing piston, communicating with said outlet passage, urged in one direction in response to fluid pressure in said passage and urged in the opposite direction by a spring bearing on said control device, said sensing device having a port communicable with said outlet passage in preselected positions for diverting fluid from said actuator piston.

9. In hydraulic apparatus:

an adjustable pump;

a moveable control for said pump effective to modify the delivery of said pump in accordance with the position of said control;

a fluid operated bias piston urging said control in one direction;

an inlet fluid pressure passage communicating With said bias piston;

an outlet fluid passage;

a first orifice interconnecting said inlet and outlet passages;

a second orifice connected to said outlet passage;

a fluid operated actuator piston, communicating with said second orifice, urging said control in the other direction;

a relief passage communicating said actuator piston;

and

a sensing device movable to a position to block said relief passage, said sensing device being shiftable in one direction responsive to fluid pressure in said outlet passage and being shifta'ble in the other direction by a spring bearing on said control device.

References Cited UNITED STATES PATENTS 2,552,604 5/1951 Thoma 6052 2,605,709 8/1952 Jubb 1031 X 2,648,312 8/1953 Tucker et a1. 10338 X 2,669,935 2/1954 Tucker 103-38 2,892,312 6/1959 Allen et al. 60-52 2,903,852 9/1959 Bottoms 103162 X 3,213,805 10/1965 Cooper et al. 103162 FOREIGN PATENTS 1,269,287 7/1961 France.

ROBERT A. OLEARY, Primary Examiner.

WILLIAM L. FREEH, DONLEY J. STOCKING,

Examiners. 

